A centrifugal separator according to the following description is known and includes a stationary part forming a base, non-rotating part, which includes a bracket and which is elastically connected to the stationary part by means of an elastic connection, and a rotating part which is configured to rotate around an axis of rotation and includes a centrifuge rotor. The centrifuge rotor includes a rotor casing, which forms an inner separation space, and a rotating bearing-receiving element in the form a spindle. The centrifuge rotor includes a disk package with a plurality of separating disks. The rotating part is journalled in a stiff manner in the non-rotating part in such a way that the rotating part and the non-rotating part are commonly pivotable in relation to the stationary part by means of the elastic connection. A drive arrangement drives the rotating part to rotate around the axis of rotation within a range of revolutions, which extends from zero to a highest number of revolutions per minute and which includes at least one operating number of revolutions. An inlet channel extends into the inner separation space for feeding of a medium to be separated. An outlet channel, which is fixedly attached to the stationary part, extends out from the inner separation space for discharge of a separated product.
Another similar separator is also known wherein the stator of the drive motor is fixedly connected to the stationary part.
Historically, centrifugal separators have typically been designed with a relatively long and thin spindle, which permits the centrifuge rotor to pivot or oscillate laterally. All centrifugal separators have a number of critical numbers of revolutions at which such pivoting or lateral deflection, of the centrifuge rotor arises. It is desirable to drive centrifugal separators at relatively high rotation rates for achieving an efficient separation. These desired rotational rates are normally higher than at least the first critical rotational rate. When initiating a separation process, the first critical rotational rate thus has to be passed. Stable operation is achieved within a range of rotational rates above the first critical rotational rate.
Centrifugal separators of a conventional kind also have a limitation with regard to how high the centrifuge rotor and the disk package provided therein can be made. This limitation depends at least partly on the relation of the moments of inertia of the centrifuge rotor, i.e. between the polar moment of inertia of the centrifuge rotor and the diametrical moments of inertia of the centrifuge rotor. If this relation of moments of inertia is too small it is difficult to achieve a stable operation. It would be desirable to be able to make the centrifuge rotor higher in spite of the limitation formed by the relation of moments of inertia, since then more separating disks can be provided and the separation capacity can be increased.